Implantable cardiac pulse generators such as implantable cardiac stimulation devices (IPGs) may take the form of implantable cardioverter-defibrillators that utilize unique and rapid stimulation rates or high energy shocks to treat accelerated or chaotic rhythms of the heart in an effort to restore a normal heart rhythm. IPGs can also include pacemakers that provide low voltage stimulation to regulate the heart rate in the setting of a bradycardia. In addition to providing therapeutic stimulation, these IPGs include sensing circuits that sense electrical signals generated by the heart indicative of cardiac activity and memory device to store these sensed signals and data. IPGs are typically also configured to transmit stored signals and data to external devices or programmers in order to aid a diagnosis by a physician or clinician. For the purpose of this patent, an IPG represents any implantable medical device capable of monitoring one or more physiologic functions and/or delivering therapy. As such, in addition to cardiac pacemakers and cardioverter-defibrillators which are well established in the art, this also includes neurologic stimulation devices, gastric stimulation devices, implantable monitors including cardiac monitors, glucose monitors and others.
Historically, the transfer of data from the IPG to the programmer or other device was performed either in the hospital or the physician's office. Increasingly, the transfer of this data from the implantable device to an external device accessible by a physician is done in locations outside of a clinic, hospital, or other traditional medical setting. For example, a patient having an IPG may also have a remote monitoring unit (RMU) in their home that automatically communicates with the IPG to wirelessly download data acquired by the IPG. Data acquired by the RMU may be transferred over a network to a remote server so that it is accessible to a physician or a clinician at a remote medical site.
However, RMUs fail to handle many dangerous events and the general transfer of data efficiently. For example, a typical RMU located in a patient's home may operate by downloading information obtained and stored on the IPG at regular intervals. However, an event (e.g., a patient's medical condition) may occur shortly after the previous download and this event would not be acquired by the system until the next scheduled download. In the case that the event represents a problem with the IPG or a patient emergency, the proper medical professional may not be alerted quickly when another scheduled download is not for some time. This may put the patient at risk when a problem is being experienced and they are unable to either detect or inform a physician or emergency medical technician themselves.
One current solution to this problem used with some RMUs is to increase the frequency at which data transfers occur. If the RMU downloads information from the IPG more frequently, then the average time between an event and data collection will decrease. However, the frequent transfer of information from the implanted device and the monitoring system may reduce the battery life of the IPG because of the increased power requirements of the more frequent wireless transfer of information. When there is no meaningful event to report, this excessive transfer of information is inefficient and needlessly reduces battery life as well as potentially overloads the memory of the server or the RMU. Additionally, the drain on the battery becomes worse as the time between transfers decreases, forcing a trade-off with this solution between device life and safe monitoring of the patient. Even in circumstances where the download frequency has not been increased, valuable battery power may be used to implement preplanned downloads that contain information of limited value. Generally, implantable cardiac stimulation devices that have download capability are programmed to download at regular intervals. However, some patients may have relatively stable cardiac conditions such that the information being downloaded provides no real new information to the treating physician. In this circumstance, battery power is being consumed to provide information of limited value. Conserving battery power is, of course, of great concern with implanted devices as IPG replacement due to battery depletion typically involves an invasive medical procedure.
Thus, there is a need in the art for a system that more efficiently provides information obtained by an IPG to a RMU. There is a need in the art for a system that is able to quickly alert a physician or emergency medical technician to the occurrence of a major event, while limiting downloads and drain on battery power when the downloaded information does not warrant the power expense.